Homogeneous polyolefin and arylvinyl-polymer-based compositions

ABSTRACT

This invention concerns a process for obtaining homogeneous polymer compositions containing at least one olefin polymer and/or one arylvinyl polymer. 
     The process consists of adding, to either or to a mixture of both of these polymers, one or more block copolymers, containing one polyolefin and one polyarylvinyl sequence. 
     These polymer compositions provide homogeneous substances with properties combining those of the individual polymers, and in some mixtures these properties are considerably improved as the result of synergic phenomena.

This is a division of application Ser. No. 211,667 filed on Dec. 23,1971, now U.S. Pat. No. 3,894,117.

This invention concerns a process for preparing homogeneous polymercompositions containing at least one polymer from the olefin andarylvinyl group, and in particular a mixture of an olefin polymer, suchas polyethylene or polypropylene, with an arylvinyl polymer, such aspolystyrene. It also concerns the polymer compositions obtained by thisprocess.

There is an obvious advantage in substances which combine the propertiesof polyolefins with certain properties of polystyrene, particularly itsrigidity and suitability as a printing base.

However, because of the incompatibility of polyolefins and polystyrene,composites of these polymers are heterogeneous in structure andmechanically weak, so that it is little use preparing them.

Research has now revealed a process for obtaining, among other things,homogeneous mixtures of polyolefins and polystyrene.

The process according to the invention, for the preparation ofhomogeneous polymer compositions containing at least one polymer fromthe olefin and arylvinyl group, is characterized by the fact that thepolymer is mixed intimately with one or more block copolymers containingone polyolefin and one polyarylvinyl sequence.

In one embodiment of the invention, at least one of the block copolymersincludes a sequence formed from the polymer to which it is added.

In another embodiment of the invention, the block copolymer orcopolymers are added to a mixture of an olefin polymer and arylvinylpolymer, and each contains one sequence formed from the olefin polymerand another sequence formed from the arylvinyl polymer.

The block copolymers used in the invention can be obtained by firstpolymerizing an olefin in the presence of dialkyl-zinc and co-ordinatingcatalysts and then polymerizing the arylvinyl monomer, using aradical-type catalyst, in the presence of the non-deactivated polymerproduced during the first stage.

In one embodiment of the invention, the block copolymer is added bybeing mixed in a molten state with one of the polymers, after which theremaining polymer or polymers are added to this mixture.

In another embodiment of the invention, the block copolymers are addedto the polymer or a mixture of polymers by being mixed in a moltenstate.

In a recommended embodiment of the invention, the block copolymer orcopolymers are added to the mixture of polymers by being mixed in amolten state, under temperature and shearing conditions at which thepolymers have similar viscosities.

In another embodiment of the invention, the block polymer is added to amixture of from 50 to 100 % of one polymer and from 50 to 0 % of anotherpolymer.

In another embodiment of the invention, between 1 and 400, andpreferably 5 and 200, parts of block copolymer are added to 100 parts ofpolymer or mixture of polymers.

In another embodiment of the invention, the olefin polymers are one ormore substances such as high-density polyethylene, low-densitypolyethylene, polypropylene, polybutene, polymethylpentene,ethylene/propylene block copolymers, polyallomers, and olefin and vinylmonomer copolymers, such as ethylene/vinyl-acetate copolymers.

In another embodiment of the invention, the arylvinyl polymers are oneor more polymers obtained by polymerizing or copolymerizing styrene orstyrene derivatives.

In another embodiment of the invention, the polymers consist ofpolyethylene and polystyrene, and the block copolymer is formed from onesequence of each of them.

In another embodiment of the invention, substances such as fillers,stabilizers, plasticizers, organic or inorganic pigments, opaquingagents, or even another polymer, are added to the polymer or mixture ofpolymers before or after the block copolymer is added.

In another embodiment of the invention, the block polymer is added in amolten state, using a screw mixer, internal mixer or stirrer reactor.

In another embodiment of the invention, the block copolymer is added bymixing dry powders or granules of the polymer or polymers and of theblock copolymer.

In another embodiment of the invention, the block copolymer is added tothe polymer or polymers in solution.

This invention also concerns the homogeneous polymer compositionsobtained by this process.

It also concerns films, plates, flat or corrugated sheets, sheaths,pipes, bottles and other manufactured articles obtained from thesepolymer compositions.

Other aims and benefits will appear from the following examples ofvarious embodiments of the invention, which, however, is not confined tothem.

To simplify matters, polyethylene will be referred to below as PE, andpolystyrene as PS. In most cases, the exact trade names of thesesubstances are given in brackets. Manolene 6001 is a high-density PEwith a density of 0.96 and melt index of 0.1, and Lacqtene 1020 is alow-density PE with a density of 0.92 and melt index of 2. Lacqrenes arecrystal PEs marketed by the applicant's assignee. Polymer compositionsaccording to the invention may be used to manufacture extruded sheaths(thin films or sheets to replace paper, corrugated sheets to replacecardboard) or hollow tubing (pipes or cables), or heat-shaped orinjected articles (bottles).

For example, PE/PS/block PE.PS compositions in the form of thin sheetscan usefully replace paper, since the very fine dispersion of PS in thePE matrix gives the material touch, printing, tear-strength, flexibilityand welding properties lacking in composites that do not contain anyblock copolymer.

Sheets of excellent quality for printing work can be obtained fromcomposites containing 5 to 30 weight percent of block copolymers, 2 to40 % PS, and the rest PE, and possibly including titanium oxide, withoutany preliminary treatment.

Composites with a higher block copolymer content, and particularly lowdensity polyethylene containing 20 to 50 weight percent of blockcopolymers, can be used to make articles such as bottles and pipes,which have great rigidity, not unlike that of high-density polyethylene.Composites containing these block copolymers are also found to congealmore quickly when molten than polyethylene, so that extrusion, injectionand heat-shaping processes can be speeded up.

EXAMPLE 1

The products are mixed in a double-screw welding extruder, in which thescrews rotate at a speed of 100 rpm. The mixing temperature is 200°C.

The extruded product is granulated and injected into a Battenfeld 10VP.25 plasticizer screw-press.

Two mixtures are prepared. Mixture A contains 12.5 parts weight of PE(Manolene 6001), 12.5 parts crystal polystyrene (Lacqrene 506), and 75parts PE/PS block copolymer with 20 % weight of PS.

Mixture B contains 72.5 parts weight of PE (Manolene 6001), and 27.5parts PS (Lacqrene).

Table 1 below shows the mechanical properties of each of these polymercompositions.

                                      Table 1                                     __________________________________________________________________________         Yield point                                                                          Breaking                                                                             Impact tension                                                                        Dynstat bending                                    Mixture                                                                            kg/sq.cm                                                                             elongation %                                                                         kgcm/sq.cm                                                                            kg/cm                                              __________________________________________________________________________    A    370    54     270     7.4                                                B    369    27      95     5.6                                                __________________________________________________________________________

In addition, microphotographic examination, using hot-pressedcross-sections cut with a microtome, 15 μ thick, shows that the ternarymixture is much more homogeneous than the binary mixture.

EXAMPLE 2

Using the same technique as in example 1, two more mixtures areprepared, with the following compositions by weight:

Mixture C: 60 % PE (Lacqtene 1020); 17.7 % PS (Lacqrene 550); 22.3 %PE/PS block copolymer containing 17 % PS;

Mixture D: 60 % PE (Lacqtene 1020); 24 % PS (Lacqrene 550); 16 % PE(Manolene 6001).

In the case of mixture C, the block copolymer is first mixed with thePS, and the resulting mixture added to the PE.

Microscopic examination reveals the excellent dispersion of PS inmixture C, compared with mixture D (grains <3 μ for C, 10 to 100 μ forD).

The two mixtures were extruded into sheaths, with maximum encouragementof bi-orientation (width 50 to 55 cm; thickness 10/100ths mm).

Table 2 shows the properties of these sheaths.

                  Table 2                                                         ______________________________________                                        Mixture                 C        D                                            ______________________________________                                        Surface feel            Soft     Rough                                        Dart-test in g.sup.(1) (ASTA D 1709.62T)                                                              38.5     <15                                          % breaking elongation.sup.(2)                                                                         50       26                                           Breaking strength in kg/sq.cm.sup.(3)                                                                 160      160                                          Welding properties      Good     Poor                                         Printing qualities      Good     Fair                                         ______________________________________                                         .sup.(1) For guidance, the dart-test result for a sheet of paper is 15 g.     .sup.(2) Measured parallel to direction of extrusion.                         .sup.(3) The breaking strength in the ultimate strength in the zone of        elasticity.                                                              

EXAMPLE 3

Using the technique described in example 2 for mixture C, four moremixtures are prepared. Table 3 shows the compositions of these mixturesby percentage weight.

                                      Table 3                                     __________________________________________________________________________                               PE/PS block                                                                   copolymer with                                     Mixture                                                                            PE (Lacqtene 1020)                                                                       PS (Lacqrene 550)                                                                        17 % PS                                            __________________________________________________________________________    E    65          0         35                                                 F    73         12         15                                                 G    60         20         20                                                 H    50         30         20                                                 __________________________________________________________________________

Microscopic examination shows the excellent dispersion of the PS inthese mixtures.

The mixtures were extruded into sheaths 1/10 mm thick, with an expansionrate of 3.

Table 4 shows the properties of the sheaths.

The thin sheets obtained from these mixtures resemble paper, with regardto printing qualities and surface feel. In addition, the sheets obtainedfrom mixture H have the same tearing and crumpling qualities ashigh-quality paper. No blocking occurred in any of the sheets.

                                      Table 4                                     __________________________________________________________________________               Breaking                                                                             Breaking                                                         Dart-test                                                                           strength                                                                             elongation                                                                          Welding                                                                             Appearance of                                   Mixture                                                                            in g  in kg/sq.cm                                                                          %.sup.(1)                                                                           properties                                                                          sheets                                          __________________________________________________________________________    E    106   150    370   Excellent                                                                           Very smooth                                     F    60    130    295   Excellent                                                                           Very smooth                                     G    30    215     46   Good  Soft                                            H    20    325     60   Good  Slightly rough                                  __________________________________________________________________________     .sup.(1) Measured parallel to direction of extrusion.                    

Each of these mixtures is extruded, using a die imitating thecross-section of corrugated cardboard. The resulting products have highcompressive strength, weigh 400 to 650 g/sq.m depending on thickness,and show permanent deformation when folded.

Containers are also produced by extrusion-blowing, using a 6 cm-diameterdie. The bottles obtained have good join-lines, satisfactory appearance,and high rigidity.

Test-samples produced from these mixtures show high surface-crackingstrength, measured in accordance with ASTM standard D 1693. The Vicattemperatures are 100°C for mixture E, 91°C for F, 95°C for G and 97°Cfor H. (In comparison, the Vicat temperature of low-densitypolyethylene, measured under the same conditions, is 90°C.)

Tubing, measuring 6 × 8, is also extruded using mixture E. The tube hasexcellent rigidity, and a remarkably smooth appearance. Burstingstrength at 20°C is at least twice that of polyethylene tubes producedunder the same conditions.

In addition, all these composites are much easier to extrude, and can bedrawn much faster.

EXAMPLE 4

Using the same mixing technique as for example 1, two more mixtures areprepared, mixture I, consisting of 99.4 % weight of ethylene/vinylacetate copolymer with 5 % vinyl acetate, and 0.6 % PE/PS blockcopolymers with 20 % weight of PS, and mixture J, consisting of 99.7 %weight of the same ethylene/vinyl acetate copolymer as in mixture I, and0.3 % silica gel, normally used as an agent to reduce post-extrusionblocking between sheaths made from ethylene polymers and copolymers.

The two mixtures, and the original ethylene/vinyl acetate copolymer (K),are extruded in sheaths approximately 50 cm wide and 0.05 mm thick, andtested.

Table 5 shows the results of these tests.

                  Table 5                                                         ______________________________________                                        Composite                                                                             Haze %.sup.(1)                                                                           Blocking in g.sup.(2)                                                                       Dart-test in g.                              ______________________________________                                        I       16         250           590                                          J       22         250           550                                          K        16.5      500           600                                          ______________________________________                                         .sup.(1) ASTM method.                                                         .sup.(2) Force in grams needed to detach two superimposed sheaths.       

These results show that the addition of the PE/PS block copolymer to theethylene/vinyl acetate copolymer considerably reduces post-extrusionblocking, while altering the optical and mechanical properties of theethylene/vinyl acetate copolymer as little as possible.

Polyolefin/polyarylvinyl and particularly polyethylene/polystyrene blockcopolymers therefore act as an anti-blocking agent in olefin polymerssuch as polyethylene, or olefin copolymers such as ethylene/vinylacetate copolymer, used to manufacture extruded sheaths and films.

When less than 10 weight percent of block copolymer is added topolyolefins or olefin copolymers, such as ethylene/vinyl acetatecopolymer, the block copolymer confers considerable slipping power onthe films and sheaths manufactured. In other words, the block copolymercan be used to replace the slip agent, such as fatty amide, normallyused for this purpose.

Naturally, the invention is in no way confined to those examples: manyalternative forms are possible, for someone skilled in the art,depending on the applications involved, without any departure from thespirit of the invention.

What is claimed is:
 1. A homogeneous polymer composition comprising onemember of the group consisting of monoolefin polymer and polystyrene,and at least one polymonoolefin-polystyrene block copolymer containingone polymonoolefin and one polystyrene sequence wherein said blockcopolymer is present in an amount of 0.6 % to 80 % based on the totalweight of said block copolymer and said member of the group.
 2. Thehomogeneous polymer composition of claim 1 wherein said group consistsof polyethylene, polypropylene, polybutene, polymethylpentene,ethylene/propylene block copolymer, ethylene/vinyl acetate copolymer,and polystyrene.
 3. The homogeneous polymer composition of claim 1comprising low density polyethylene and 20 to 50 weight percent blockcopolymer.
 4. The homogeneous polymer composition of claim 1 wherein themember of the group is an ethylene/vinyl acetate copolymer.
 5. Thehomogeneous polymer composition of claim 1 wherein the amount of blockcopolymer is less than 10 weight percent.